There are numerous sources of water contamination in hydrocarbon liquid fuels. Trace amounts of water exist in fuel due to the refining and purification processes performed at the petroleum refineries. Next, water may seep into gasolene storage tanks or may form as condensation in storage tanks or delivery trucks. Additionally, when gasolene or other liquid fuels are placed in the fuel tanks of vehicles or boats, water may form through condensation, or may be inadvertently introduced into the tank, particularly in marine environments. As a result, virtually all liquid fuel used to power automotive, diesel or marine engines contain a fractional amount of water when it is introduced into the engine for combustion.
The practical necessity for conditioning fuel drawn from a fuel tank prior to introduction into an internal combustion engine is well known, particularly in marine engines and diesel engines. Most automotive gasoline-fueled engines can accommodate relatively large amounts of water before problems such as poor drivability and stalling occur. However, diesel-type engines which are powered by fuel oil are much less tolerant of water mixed with fuel. Normally, these engines utilize pumps and fuel injection devices for introducing pressurized fuel to the engine. As compared to carburetors, the pump and injectors are expensive devices and are sensitive to water which has an undesirable corrosive effect on this equipment. Corrosive reactions within the working components of internal combustion engines can cause such problems as rust, clogged fuel components, fuel pumps that freeze up, and damaged fuel injectors. From a performance standpoint, water mixed with fuel can cause roughness in engine operation, loss of power, and poor starting ability, particularly when an engine is started cold. Water which settles to the bottom of the fuel tank is drawn into the fuel stream first when an engine is started so the water/fuel ratio is higher and the adverse effects are greater. Therefore it is desirable to prevent the passage of any substantial amount of water to fuel injection equipment.
Similarly, marine engines are subject to a high probability of water contamination in fuel due to the environment in which they operate. Two-cycle outboard engines in particular can suffer from severe performance degradation when fuel is contaminated by water.
Since water can be introduced into the fuel at any point in the distribution and storage process, as discussed above, the most effective way to keep water from the engine components is to separate it from the fuel just prior to fuel combustion. This is best accomplished by a filter system located in-line between the fuel tank and the fuel system components. A number of devices have been proposed for this purpose, generally using the principles of gravity separation, centrifugal separation, hygroscopic material, filter elements, or a combination thereof. For example, U.S. Pat. No. 4,860,713 to Hodgkins discloses a fuel filter which passes the fuel through a polyester fiber cylinder and into a water separator chamber where the water coalesces to the bottom of the chamber due to its higher density. Similarly, the fuel-water separator disclosed in U.S. Pat. No. 4,334,989 to Hall uses fluid impervious material enclosed within a chamber to diffuse the flow of fuel through the supply line so that any water mixed with the fuel tends to descend to the bottom of the chamber due to its greater specific gravity. The fuel-water separator of U.S. Pat. No. 4,257,890 to Hurner directs incoming fuel into an inlet chamber located inside a fine stainless steel conical mesh screen, where the heavier water migrates towards the bottom of the chamber and the fuel passes through the screen. In another approach disclosed in U.S. Pat. No. 4,795,556 to Brotea, fuel is passed through a housing containing tightly packed granules of hygroscopic material such as calcium sulfate hydrate or calcium chloride which retain water but allow fuel to pass through. In yet another approach disclosed in U.S. Pat. No. 4,384,962 to Harris, centrifugal force is used to separate water from the relatively lighter fuel. Each of the referenced devices has several drawbacks. Gravity and centrifugal separators are generally large, expensive and inefficient, and generally require mounting the separator vertically such that the water collects at the bottom of the device. Filter elements such as paper attract water, but are inefficient, will only remove a small percentage of their weight in water, and clog easily, allowing the water to form a film which impedes fuel flow through the element. The hygroscopic material separators are similarly large, expensive and require frequent replacement of the hygroscopic drying agent.
Other materials such as petroleum sorbents which have been developed in the last few years offer unique qualities often used in oil spill containment applications. Sorbents recover petroleum products by either adsorption in which the petroleum is attracted to the sorbent surface and then adhered to it, or absorption in which the petroleum penetrates the pores of the sorbent material. In either case, water is repelled by the sorbent material. While sorbent material may consist of natural products, recent sorbent material has consisted of synthetic products such as polyethylene or polypropylene. For example, U.S. Pat. No. 5,165,821 to Fischer discloses an oil-sorbing boom which uses a spirally wound sheet of polymeric, oleophilic, hydrophobic polypropylene microfibers. Similarly, U.S. Pat. No. 4,965,129 to Bair discloses an article for absorbing liquids which includes fine, fibrous particles of flash-spun polyethylene. U.S. Pat. No. 5,080,956 to Smith discloses an oil sorbent mat constructed of an absorbent sheet of fibrous olefin heat bonded to a nonporous sheet. U.S. Pat. No. 5,407,575 to Vinsonhaler teaches an oil spill cleanup pad comprised of polyethylene or polypropylene fibers which functions by adsorption and capillary action to transfer oil to a core of polyurethane foam; that is, the outer surface attracts and the inner core adsorbs the oil while repelling water.
Similar materials used to contain and recover leaking lubricants include oil sorbent polypropylene blown microfiber pads marketed by Minnesota Mining and Manufacturing Company under the product numbers HP-156, HP-157, HP-255, HP-256, HP-556, HP-557 and T-151. These pads, described in 3M product bulletin "Petroleum Sorbents" N. 70-0705-1759-7 (573) JR, present enormous fiber surface area which attracts petroleum while repelling water.